1. Field of the Invention
The present invention relates in general to centrifugal and mixed flow turbo-machineries (pumps, blowers and compressors), and relates in particular to a vaneless diffuser turbomachine that can operate over a wide flow rate range, by avoiding flow instability generated at low flow rates.
2. Description of the Related Art
When a centrifugal or mixed flow turbomachine is operated at low flow rates, stream separation can occur in some parts of the fluid compression system, such as impeller and diffuser, thus leading to a reduction in pressure increase factor for a given flow rate, and producing a phenomenon of flow instability (rotating stall and surge) to make the system inoperable.
A current trial to resolve this problem is to maintain minimum flow rate by providing bypass pipes or blow-off valves in the system so that the supply of fluid to the equipment to be operated is reduced. However, the volume flow in the impeller of the turbomachine remains unchanged, thus presenting a problem that the energy is being consumed wastefully.
It is an object of the present invention to provide a centrifugal or mixed flow type turbomachine, of a vaneless diffuser type, which can operate stably at low flow rates below the design flow rate, by preventing the initiation of flow instability in the system (rotating stall and surge).
The object has been achieved in a turbomachine having an impeller and a vaneless diffuser section, wherein two stabilization members are disposed in a predetermined location of the diffuser section so as to prevent a generation of unstable flow in the diffuser section during a low flow rates operation. Accordingly, a relatively simple approach is employed to avoid generating a phenomenon of reversed flow in the diffuser section, thereby providing a turbomachine that can operate efficiently at a lower overall cost. Also, only two stabilizing members in the diffuser prevent the head coefficient in the turbomachine from being decreased.
The stabilization member may be formed as a plate member.
The plate member may be installed so as to span across an entire width of a fluid flow path of the diffuser section.
In the turbomachine, a height dimension of the plate member may be smaller than a width dimension of a fluid flow path of the diffuser section so as to provide a space between the plate member and an opposing wall surface of the diffuser section. A suitable amount of space is effective to suppress the reversed flow in the diffuser section.
The stabilization member maybe inserted into or retracted away from the diffuser section by plate driver means.
The plate member may have a height h which is related to a width dimension b3 of the diffuser section according to a relation, h/b3 greater than 0.5.
The plate member may be aligned at an angle greater than that of a stream flowing at a rotating stall initiating flow rate into the diffuser section.